1999:251 - KILMAINHAM: 7–11 Mount Brown, Dublin

A series of test-trenches was opened up to the rear of Nos 7–11 Mount Brown, Kilmainham, on 23 June 1999. Three staggered cuttings were dug to the rear of Nos 11 and 10. It was not possible to cut a continuous trench because of water seepage from the Cammock River, situated immediately to the north. The three cuttings were opened to an average depth of 1–2m. The base consisted of yellow daub and loose gravel, consistent with an undisturbed natural ground surface. This was overlain in each trench by a heavy layer of riverine silt averaging 1m deep. The upper layer was consistent with garden soil and debris of 19th- and 20th-century date.

A second series of three staggered cuttings was dug to the rear of No. 8. Cutting A was c. 3m from the end wall of the plot, which abuts the southern edge of the Cammock River. It extended southwards for a distance of 5.8m. A natural daub and gravel horizon was present at a depth of 2.2m. This is overlain by a silt deposit averaging 1.2m thick. A mortared wall, orientated east-west, cuts through the cutting at the north. Its present surface is 1m below ground level, and it extends to a depth of c. 0.8m. A brick-lined sewer extends the entire length of the western section of the cutting. It lies immediately below the concrete ground surface.

During the testing, a series of wooden structures was identified in the rear yard of No. 8 Mount Brown. It appeared to be the remains of two rectangular timber pits or tanks. A clear section of one of the pits was exposed, and part of a second one. Each structure contained a 0.4m-thick deposit of mulch containing wood bark at the base. The structure is made up of vertical square posts with horizontal planking for the sides and base. Some of the base timbers were partly damaged by the digger. The planks and post appear to be of planed timber, and the planks themselves are nailed very tightly and neatly together using what appear to be hand-forged nails of 18th/19th-century type. A sample of wood bark was retrieved from the mulch deposit. It contained an acorn fragment, which suggests that at least some of the bark is oak.

A second 6m-long trench was dug to the rear of No. 8, and a wooden structure was identified close to the surface. It is similar to that previously described and consists of two, possibly three, pits or tanks that extend almost the entire length of the cutting. The walls are made of tightly fitting lengths of planed timber laid horizontally and nailed together using hand-forged nails. They are in turn nailed to upright posts that are square in section. A series of three wooden dividers was present, forming three separate pits or tanks. These were defined by square upright posts of planed timber onto which the horizontal timbers are laid. The central chamber has a tightly fitting planked bottom. It is present at a depth of 1.6m below present ground level. This chamber was filled to a depth of 0.5m with a mulch containing wood bark fragments. The easternmost chamber does not appear to have any bottom, is silt-filled and does not contain a mulch deposit. Its eastern wall face is wooden but has a central gap resembling a sluice-gate of some kind. There appears to be at least one surviving groove to hold a thin sectioned cross timber. The entire wooden structure is cut into the silt layer.

Following the identification of these wooden structures, a full excavation of the rear of No. 8 was undertaken in July 1999. The excavation exposed a two-phase use of the site. The earlier phase consisted of a series of wooden tanning tanks or pits that extended the entire area of the rear yard of No. 8. Two sets of tanks were identified, one larger than the other, separated by a narrow aisle. A number of the wooden tanks extend eastwards into the adjoining property of No. 7 (known as the Band Hall). Narrow gaps in the stonework along the party wall were consistent in size and orientation with the end timbers of the wooden tanks, indicating that the western wall of the Band Hall had been constructed around and over the wooden tanks and had thereby cut through a number of them.

All of these tanks contained an organic mulch deposit. One of the smaller tanks is now part of the National Museum of Ireland's Folklife collection. An examination of this tank revealed that the base timbers were nailed from the base, which indicates that the tanks were not built in situ.

The second phase of industrial use on the site consisted of a series of brick tanks. These were built directly on top of the wooden tanks, and in some cases the upper timbers of the wooden tanks were deliberately cut or broken to facilitate the brick tanks. Four of the tanks were connected and were situated at the southern end of the yard. The contents of these tanks indicate that they were used to hold early 20th-century coal and refuse. The primary deposits in each tank, however, consisted of a rope-like fabric that overlay but was partly embedded in the surface of a thick, white deposit of lime. The fabric/rope may have been undergoing some industrial process in these tanks. The presence of lime in the base of the four tanks may be associated with the cleaning of animal hides.

The remaining two were large, single, brick tanks. Both abutted the wall that divided the yard from the Cammock River. One was situated in the north-west corner of the yard. It had an outflow opening with a blocking mechanism at floor level. It also contained a false floor of timber planks. These were the same as the planks used in the wooden tanks and were probably reused here. The base of this tank contained a shallow deposit of light green sludge. The second tank is situated in the north-east corner of the site abutting the river. It was not fully investigated, as part of it appears to extend under the adjoining property of No. 7 Mount Brown. This is significant in terms of establishing a dating sequence because that building, which now houses the Band Hall, was present on an early 19th-century Ordnance Survey map of the area.

This is a tannning yard. Members of the Shannon family were tanners in the Kilmainham area from at least the late 18th century and are listed in various Dublin directories as occupiers of houses in Mount Brown in the early 19th century. Leather-making involves three processes, whereby animal skins are cleaned, tanned and dressed. Tanning is often a highly polluting process that requires a water source, and the Cammock River, immediately to the rear of the yard, is likely to have been the reason for siting the tannery here. There are two ways by which tanning may be effected, using either vegetable tannins or chromium salts. In this case vegetable tanning was used. It involves the soaking of prepared skins in tannic acid. This acid occurs in the bark, wood, fruit and galls of certain trees such as the oak. The function of the tannic acid is essential in the manufacture of leather from hides in that it precipitates gelatine to give an insoluble compound.

The identification of an acorn within the bark fill of the wooden structure in Trench A is consistent with an interpretation that these are soaking pits containing tannic acids in which hides were immersed. The well-preserved condition of the timbers and the position of the structures in the silt layer are also consistent with this view.

The entire area is not yet archaeologically resolved because of access and ownership issues, and it is hoped because of this to return in 2000.

45 Daniel Street, Dublin 8